U.S. patent application number 10/681157 was filed with the patent office on 2004-05-13 for bipolar battery.
This patent application is currently assigned to NISSAN MOTOR CO., LTD.. Invention is credited to Fukuzawa, Tatsuhiro, Hosaka, Kenji, Nemoto, Kouichi.
Application Number | 20040091771 10/681157 |
Document ID | / |
Family ID | 32105477 |
Filed Date | 2004-05-13 |
United States Patent
Application |
20040091771 |
Kind Code |
A1 |
Hosaka, Kenji ; et
al. |
May 13, 2004 |
Bipolar battery
Abstract
A bipolar battery comprises a bipolar electrode in which a
positive electrode is provided on one surface of a collector and a
negative electrode is provided on the other surface of the
collector, a gel electrolyte sandwiched between the positive
electrode and the negative electrode, and a sealing layer which is
provided between the collectors and surrounds a periphery of a
single cell including the positive electrode, the negative
electrode, and the gel electrolyte.
Inventors: |
Hosaka, Kenji;
(Yokosuka-shi, JP) ; Fukuzawa, Tatsuhiro;
(Yokohama-shi, JP) ; Nemoto, Kouichi; (Zushi-shi,
JP) |
Correspondence
Address: |
McDERMOTT, WILL & EMERY
600 13th Street, N.W.
Washington
DC
20005-3096
US
|
Assignee: |
NISSAN MOTOR CO., LTD.
|
Family ID: |
32105477 |
Appl. No.: |
10/681157 |
Filed: |
October 9, 2003 |
Current U.S.
Class: |
429/185 ;
29/623.2; 429/162; 429/210; 429/300 |
Current CPC
Class: |
H01M 10/0585 20130101;
H01M 10/0565 20130101; Y10T 29/4911 20150115; H01M 4/485 20130101;
H01M 4/587 20130101; Y02P 70/50 20151101; H01M 10/0525 20130101;
Y02E 60/10 20130101; H01M 6/48 20130101; H01M 4/5825 20130101; H01M
10/0418 20130101; H01M 2300/0082 20130101; H01M 50/183 20210101;
H01M 4/48 20130101 |
Class at
Publication: |
429/185 ;
429/300; 429/210; 029/623.2; 429/162 |
International
Class: |
H01M 002/08; H01M
006/48; H01M 006/22; H01M 006/46 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 7, 2002 |
JP |
P2002-323971 |
Claims
What is claimed is:
1. A bipolar battery, comprising: a bipolar electrode in which a
positive electrode is provided on one surface of a collector, and a
negative electrode is provided on the other surface of the
collector; a gel electrolyte sandwiched between the positive
electrode and the negative electrode; and a sealing layer which is
provided between the collectors and surrounds a periphery of a
single cell including the positive electrode, the negative
electrode, and the gel electrolyte.
2. A bipolar battery according to claim 1, wherein the sealing
layer is made of first resin provided to be positioned on sides of
the collectors and non-conductive second resin which is sandwiched
by the first resin and has a higher melting point than that of the
first resin, and the collectors and the sealing layer are thermally
welded at temperature between melting points of the first resin and
the second resin.
3. A bipolar battery according to claim 2, wherein an electrode
stacked body is formed by stacking a plurality of the bipolar
electrodes, the gel electrolytes and the sealing layers, and the
melting point of the first resin becomes higher as it is positioned
further outside the electrode stacked body.
4. A bipolar battery according to claim 2, wherein the first resin
and the second resin are at least two resins, which have a higher
melting point and a lower melting point than the temperature of the
thermal welding, respectively, and which are selected from a group
containing polypropylene, polyethylene, polyurethane, thermoplastic
olefin rubber, polyamide-based resin, polytetrafluoroethylene,
polyvinylidene fluoride, polystyrene and silicone rubber.
5. A bipolar battery according to claim 1, wherein the positive
electrode includes composite oxide of lithium and transition metal,
and the negative electrode includes carbon or composite oxide of
lithium and transition metal.
6. An assembled battery, comprising: a plurality of bipolar battery
connected in series and/or in parallel, the bipolar battery,
comprising: a bipolar electrode in which a positive electrode is
provided on one surface of a collector, and a negative electrode is
provided on the other surface of the collector; a gel electrolyte
sandwiched between the positive electrode and the negative
electrode; and a sealing layer which is provided between the
collectors and surrounds a periphery of a single cell including the
positive electrode, the negative electrode, and the gel
electrolyte.
7. A vehicle, comprising an assembled battery including a plurality
of bipolar battery connected in series and/or in parallel, the
bipolar battery comprising: a bipolar electrode in which a positive
electrode is provided on one surface of a collector, and a negative
electrode is provided on the other surface of the collector; a gel
electrolyte sandwiched between the positive electrode and the
negative electrode; and a sealing layer which is provided between
the collectors and surrounds a periphery of a single cell including
the positive electrode, the negative electrode, and the gel
electrolyte.
8. A method for manufacturing a bipolar battery, comprising:
forming a bipolar electrode in which a positive electrode is
provided on one surface of a collector and a negative electrode is
provided on the other surface of the collector; sandwiching a gel
electrolyte between the positive electrode and the negative
electrode, and simultaneously sandwiching a sealing layer between
the collectors in a periphery of a single cell including the
positive electrode, the negative electrode, and the gel
electrolyte; and heating and pressurizing a portion of the sealing
layers from sides of end collectors in a state where a plurality of
the bipolar electrodes, the gel electrolytes and the sealing layers
are stacked on each other.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a bipolar battery.
[0003] 2. Description of the Related Art
[0004] Lithium ion secondary batteries include those using a solid
electrolyte, a liquid electrolyte, and a polymer gel electrolyte,
respectively, as electrolytes to be encapsulated therein.
[0005] The lithium ion secondary battery using the solid
electrolyte is that using a solid polymer electrolyte, such as
polyethylene oxide, as the only electrolyte thereof. On the other
hand, for the liquid electrolyte, only an electrolysis solution is
used. The polymer gel electrolyte is considered to be an
intermediate of a solid electrolyte and a liquid electrolyte. The
polymer gel electrolyte includes one in which an electrolysis
solution is held among chains of polymer such as polyvinylidene
fluoride (PVDF) which has no lithium ion conductivity in itself
(refer to Japanese Patent Application Laid-Open No.
H11-204136).
SUMMARY OF THE INVENTION
[0006] However, when constructing a single cell using the polymer
gel electrolyte and stacking a plurality of the single cells to
make a bipolar battery, there has been a problem that the
electrolyte oozes between each of the single cells and contacts
with the electrolyte of another single cell, thus causing a short
circuit, called a liquid junction, between the single cells.
[0007] The present invention was made in consideration of the
above-described problems. It is an object of the present invention
to provide a bipolar battery in which the liquid junction between
the single cells is prevented even when stacking the plurality of
single cells using the polymer gel electrolyte to construct the
bipolar battery.
[0008] The first aspect of the present invention provides a bipolar
battery, comprising: a bipolar electrode in which a positive
electrode is provided on one surface of a collector, and a negative
electrode is provided on the other surface of the collector; a gel
electrolyte sandwiched between the positive electrode and the
negative electrode; and a sealing layer which is provided between
the collectors and surrounds a periphery of a single cell including
the positive electrode, the negative electrode, and the gel
electrolyte.
[0009] The second aspect of the present invention provides an
assembled battery, comprising: a plurality of bipolar battery
connected in series and/or in parallel, the bipolar battery,
comprising: a bipolar electrode in which a positive electrode is
provided on one surface of a collector, and a negative electrode is
provided on the other surface of the collector; a gel electrolyte
sandwiched between the positive electrode and the negative
electrode; and a sealing layer which is provided between the
collectors and surrounds a periphery of a single cell including the
positive electrode, the negative electrode, and the gel
electrolyte.
[0010] The third aspect of the present invention provides a
vehicle, comprising an assembled battery including a plurality of
bipolar battery connected in series and/or in parallel, the bipolar
battery comprising: a bipolar electrode in which a positive
electrode is provided on one surface of a collector, and a negative
electrode is provided on the other surface of the collector; a gel
electrolyte sandwiched between the positive electrode and the
negative electrode; and a sealing layer which is provided between
the collectors and surrounds a periphery of a single cell including
the positive electrode, the negative electrode, and the gel
electrolyte.
[0011] The fourth aspect of the present invention provides a method
for manufacturing a bipolar battery, comprising: forming a bipolar
electrode in which a positive electrode is provided on one surface
of a collector and a negative electrode is provided on the other
surface of the collector; sandwiching a gel electrolyte between the
positive electrode and the negative electrode, and simultaneously
sandwiching a sealing layer between the collectors in a periphery
of a single cell including the positive electrode, the negative
electrode, and the gel electrolyte; and heating and pressurizing a
portion of the sealing layers from sides of end collectors in a
state where a plurality of the bipolar electrodes, the gel
electrolytes and the sealing layers are stacked on each other.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The invention will now be described with reference to the
accompanying drawings wherein;
[0013] FIG. 1 is a cross-sectional view illustrating a structure of
an electrode stacked body of a bipolar battery according to the
present invention;
[0014] FIG. 2 is a partially enlarged view illustrating a single
cell of the bipolar battery according to the present invention;
[0015] FIG. 3 is a cross-sectional view illustrating a method for
manufacturing the electrode stacked body of the bipolar battery
according to the present invention;
[0016] FIG. 4 is a perspective view illustrating the bipolar
battery of the present invention;
[0017] FIG. 5 is a cross sectional view taken on line V-V of FIG.
4;
[0018] FIG. 6A and 6B are views illustrating structures of sealing
layers used in the adhesive strength test;
[0019] FIG. 7 is a view illustrating a result of the adhesive
strength test;
[0020] FIG. 8 is a perspective view illustrating an assembled
battery applying the bipolar battery of the present invention;
[0021] FIG. 9 is a top plan view illustrating an inner structure of
the assembled battery applying the bipolar battery of the present
invention;
[0022] FIG. 10 is a perspective view illustrating an assembled
battery module applying the bipolar battery of the present
invention; and
[0023] FIG. 11 is a view illustrating a vehicle having the
assembled battery module applying the bipolar battery of the
present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] Hereinafter, description will be made of embodiments of the
present invention with reference to the drawings.
[0025] As shown in FIGS. 1 to 3, in the bipolar battery of the
present invention, a positive electrode layer 3 and a negative
electrode layer 4 are respectively formed on each surface of a
collector 2. The positive electrode layer 3 and the negative
electrode layer 4 on the collector 2 sandwich an electrolyte layer
5 to construct a single cell 6. This bipolar battery includes an
electrode stacked body 1 in which a plurality of the single cells 6
is stacked. Collectors 7 (also referred to as end collectors 7) at
both ends in a stacked direction have a structure in which either
the positive electrode layer 3 or the negative electrode layer 4 is
formed. Here, the structure in which the positive electrode layer 3
and the negative electrode layer 4 are provided on the collector 2
is called a bipolar electrode.
[0026] The electrolyte layer 5 used herein is a gel electrolyte in
which an amount from a little to 98 wt % of an electrolysis
solution is held among polymer chains. In this embodiment in
particular, a polymer gel electrolyte holding 70 wt % or more of
the electrolysis solution can be used.
[0027] In this bipolar battery, in order to prevent liquid leakage
from the single cells 6, sealing layers 9 are provided, which are
placed between each of the collectors 2 and 7, and surround the
peripheries of the respective single cells 6.
[0028] The sealing layer 9 is constructed by first resin 10 which
has a low melting point and is thermally adhesive and second resin
11 which is non-conductive and has a higher melting point than that
of the first resin 10. As shown in FIG. 2, the first resin 10 is
placed on the side of the collector 2, and two pieces of the first
resin 10 sandwich the second resin 11 therebetween, thus
constructing three layers. Since the sealing layer 9 is constructed
to have three layers as above, both of the collectors 2 and 7 and
the second resin 11 are thermally adhered through the first resin
10, by heating and pressurizing at a temperature higher than the
melting point of the first resin 10 and lower than that of the
second resin 11. Specifically, the first resin 10 melts during the
thermal adhesion, and bonds both collectors 2 and 7 and the second
resin 11, and then seals the electrolyte layer 5 in a space formed
by the collectors 2 and 7 as well as the sealing layer 9. Thus,
electrolyte is kept from leaking, and thereby liquid junction
between the single cells 6 is prevented.
[0029] A method of manufacturing this bipolar battery is as
follows. As shown in FIG. 3, the single cells 6 and collectors 2
and 7 are used. Each of the single cells 6 is one in which the
positive electrode layer 3 and the negative electrode layer 4, each
being formed on the collectors 2, face each other while sandwiching
the electrolyte layer 5 therebetween. The end collectors 7 have
only the positive electrode layer 3 or the negative electrode layer
4 formed thereon. The collectors 2 and 7 sandwich the sealing layer
9 therebetween at the periphery of each of the single cells 6, and
a plurality of these layers are stacked to form a electrode stacked
body 1. Then, the space formed by the collectors 2 and 7 as well as
the sealing layer 9 are sealed by pressurizing the sealing layer
portions using presses 13 while heating.
[0030] When the heating temperature is, for example, 180 degrees
centigrade, the first resin 10 is preferably a resin having a
melting point lower than 180 degrees centigrade. To be specific, a
material that can be used is thermoplastic olefin rubber or general
purpose plastic such as polypropylene (PP), polyethylene (PE), and
polyurethane. The melting point of polypropylene is about 160 to
170 degrees centigrade, the melting point of linear low density
polyethylene is about 130 degrees centigrade, and the melting point
of polyurethane is about 130 degrees centigrade. On the other hand,
the second resin 11 may be any material as long as it is a
non-conductive resin which has a melting point of about 180 degrees
centigrade or higher and can be thermally adhered to the first
resin 10. For example, polyamide-based resin such as nylon 6 and
nylon 66 can be used. In addition, for the second resin 11, it is
possible to use polytetrafluoroethylene (PTFE), polyvinylidene
fluoride, polystyrene, and the like, furthermore silicone rubber
and the like. The melting point of nylon 6 is about 225 degrees
centigrade, the melting point of nylon 66 is about 267 degrees
centigrade, the melting point of PTEF is about 320 degrees
centigrade, the melting point of polyvinylidene fluoride is about
210 degrees centigrade, and the melting point of polystyrene is
about 230 degrees centigrade. Furthermore, the silicone rubber is
usable at about 250 degrees centigrade.
[0031] Apart from the above, various resins can be used.
Preferably, the second resin 11 having a higher melting point than
that of the first resin 10 is selected, and the first and second
resin 10 and 11 are adhered by heating and pressurizing at a
temperature between the melting points thereof.
[0032] Using an electrode stacked body 1 formed in this way, a
bipolar battery 20 shown in FIGS. 4 and 5 is made. In the bipolar
battery 20, later-described positive and negative electrode
terminal plates 14 and 15 are provided on the end collectors 7 of
the electrode stacked body 1, and further, positive and negative
electrode leads 23 and 24 are connected to the positive and
negative terminal plates 14 and 15, respectively. The positive and
negative electrode leads 23 and 24 are led outside from the end
edges of battery packaging materials 16a and 16b, constructing the
positive and negative electrode leads 23 and 24, respectively.
[0033] Hereinafter, description will be given regarding the
collectors 2 and 7, the positive and negative electrode layers 3
and 4, the electrolyte layer 5, the battery packaging materials 16a
and 16b, the terminal plates 14 and 15, and the leads 23 and 24,
which can be used for this bipolar battery.
[0034] Collector
[0035] The collectors 2 and 7 have to be thin films which can be
stacked and wound. Therefore, as far as the manufacturing process
is concerned, it is preferable that the collectors are manufactured
by a thin film manufacturing technology such as spray coating. The
material therefor includes metal powder as a major constituent and
resin as a binder. For the metal powder, aluminum, copper,
titanium, nickel, stainless steel (SUS) and alloy thereof can be
used. The metal powder can be used individually, or two or more
kinds of metal powder can be mixed for use. Moreover, the binder
can be, but is not particularly limited to, a resin binder such as
epoxy resin, for example. In addition, a conductive polymer can be
used.
[0036] A manufacturing method of the collectors 2 and 7 is as
follows. First, the metal powder, the binder and the solvent are
mixed to make collector metal paste. The metal paste is then made
into a thin film by a spray coating method or the like, and the
thin film is heated. Although, collectors 2 and 7 are single
layered in many cases, they may be multi-layered, formed by
stacking collectors each containing different kind of metal powder.
A thickness of each of the collectors is not particularly limited,
but it is usually preferable that the thickness is within a range
of 1 to 100 .mu.m.
[0037] Positive Electrode Layer
[0038] The positive electrode layer 3 mainly contains a positive
electrode active material. In addition to that, an electrolyte, a
lithium salt, a conductive material and the like are contained in
order to improve ion conductivity. It is particularly preferable
that at least one of the positive and negative electrode layers 3
and 4 contains the electrolyte, preferably a solid polymer
electrolyte. In order to further improve a battery performance of
the bipolar battery, it is more preferable that the electrolyte is
contained in both of the positive and negative electrode layers 3
and 4.
[0039] For the positive electrode active material, a composite
oxide of transition metal and lithium can be used. Specifically,
the positive electrode active material may include Li--Co based
composite oxide such as LiCoO.sub.2, Li--Ni based composite oxide
such as LiNiO.sub.2, Li--Mn based composite oxide such as
LiMn.sub.2O.sub.4 having a spinel structure, and Li--Fe based
composite oxide such as LiFeO.sub.2. In addition, phosphate
compound or sulfate compound of transition metal and lithium such
as LiFePO.sub.4, transition metal oxide or sulfide such as
V.sub.2O.sub.5, MnO.sub.2, TiS.sub.2, MoS.sub.2 and MoO.sub.3, and
PbO.sub.2, AgO and NiOOH may also be included.
[0040] Considering a manufacturing process, a particle size of the
positive electrode active material is not limited as long as the
positive electrode material can be formed into paste and then into
a film by spray coating or the like. In order to further reduce
electrode resistance of the bipolar battery, it is preferable to
use the positive electrode active material with a particle size
smaller than that of the material generally used for a lithium ion
battery having a liquid electrolyte. Specifically, the preferable
mean particle size of the positive electrode active material is
within a range of 0.1 to 10 .mu.m.
[0041] For the electrolyte contained in the positive electrode
layer 3, a solid polymer electrolyte, a polymer gel electrolyte and
a stack thereof can be used. The positive electrode layer 3 can be
formed into a multi-layered construction, or formed into a layer
having different kinds of electrolytes and different kinds and
particle sizes of active materials and further, different compound
ratios thereof, on the sides of the collector and the electrolyte.
Preferably, polymer and an electrolysis solution, which are
contained in the polymer gel electrolyte, have a mass ratio of
20:80 to 98:2.
[0042] The polymer gel electrolyte is made of the solid polymer
electrolyte with ion conductivity containing the electrolysis
solution therein. Further, the polymer gel electrolyte also
includes polymer which has no lithium ion conductivity and holds
the same electrolysis solution among the chains thereof.
[0043] The electrolysis solution (an electrolyte salt and a
plasticizer) contained in the polymer gel electrolyte is not
limited as long as it is generally used for a lithium ion battery.
For example, the electrolyte salt is at least one kind of lithium
salt selected from inorganic acid salts which are LiPF.sub.6,
LiBF.sub.4, LiClO.sub.4, LiAsF.sub.6, LiTaF.sub.6, LiAlCl.sub.4 and
Li.sub.2B.sub.10Cl.sub.10, and organic acid salts such as
CF.sub.3SO.sub.3Li, (CF.sub.3SO.sub.2) .sub.2NLi and
(C.sub.2F.sub.5SO.sub.2) .sub.2NLi. The plasticizer may include,
but is not limited to, an aprotic solvent of at least one kind of
material or mixture of two or more kinds of materials selected
from: cyclic carbonates such as ethylene carbonate and propylene
carbonate; chain carbonates such as dimethyl carbonate, methyl
ethyl carbonate and diethyl carbonate; ethers such as
tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane,
1,2-dimethoxyethane and 1,2-dibutoxyethane; lactones such as
.gamma.-butyrolactone; nitrites such as acetonitrile; esters such
as methyl propionate; amides such as dimethylformamide; methyl
acetate, methyl formate and the like.
[0044] The polymer, which has no lithium ion conductivity and is
used for the polymer gel electrolyte, may include, but is not
limited to, polyvinylidene fluoride (PVDF), polyvinyl chloride
(PVC), polyacrylonitrile (PAN), polymethylmethacrylate (PMMA) and
the like. Note that it is possible to consider that PAN, PMMA and
the like could be more like polymer with ion conductivity since
they have slight ion conductivity. However, they exemplify the
polymer without lithium ion conductivity herein.
[0045] The other lithium salts contained in the positive electrode
layer 3 is, for example, inorganic acid salts such as LiPF.sub.6,
LiBF.sub.4, LiClO.sub.4, LiAsF.sub.6, LiTaF.sub.6, LiAlCl.sub.4 and
Li.sub.2B.sub.10Cl.sub.10, organic acid salts such as
(CF.sub.3SO.sub.2) .sub.2NLi and (C.sub.2F.sub.5SO.sub.2)
.sub.2NLi, and a mixture thereof, but not are limited thereto.
Further, the conductive material may include acetylene black,
carbon black, graphite and the like, but not is limited
thereto.
[0046] A compound ratio of the positive electrode active material,
the electrolyte, a lithium salt, and the conductive material should
be decided in consideration of the intended use of the battery
(prioritizing power or energy, for example) and the ion
conductivity. For example, if the compounding amount of the
electrolyte, particularly the solid polymer electrolyte is too
small in the positive electrode layer 3, resistance of ion
conductivity and ion diffusion within the positive electrode active
material layer becomes large, reducing the battery performance. On
the other hand, an excessive compounding amount of the electrolyte,
particularly solid polymer electrolyte, in the positive electrode
causes a reduction in the energy density of the battery. Therefore,
the compounding amount of the solid polymer electrolyte, which is
adequate for the purpose, is decided in view of these factors.
[0047] The thickness of the positive electrode layer 3 is not
particularly limited, but should be decided in consideration of the
intended use of the battery and ion conductivity. In general, the
thickness of the positive electrode active material layer 3 is
within a range of 10 to 500 .mu.m.
[0048] Negative Electrode Layer
[0049] The negative electrode layer 4 mainly contains a negative
electrode active material. In addition to that, an electrolyte, a
lithium salt, a conductive material and the like may be contained
for enhancing ion conductivity. Since the materials of the negative
electrode layer 4 are basically the same as those of the positive
electrode layer 3 apart from the negative electrode active
material, description thereof is omitted herein.
[0050] The negative electrode active material is preferably metal
oxide, lithium-metal composite oxide, carbon or the like, and more
preferably, carbon, transition metal oxide or lithium-transition
metal composite oxide. Yet more preferably, titanium oxide,
lithium-titanium composite oxide or carbon is used therefore. These
materials can be individually used, or two or more of them can be
used together.
[0051] Electrolyte Layer
[0052] For the electrolyte layer 5, polymer gel electrolyte is
preferably used. The electrolyte layer 5 can be multi-layered, or
formed into a layer in which different kinds of electrolytes and
different compound ratios between the components on each side of
the positive and negative electrode layers 3 and 4. When the
polymer gel electrolyte is used, polymer and an electrolysis
solution, which are contained in the polymer gel electrolyte,
preferably have a mass ratio of 20:80 to 98:2.
[0053] Such polymer gel electrolyte is made of a solid polymer
electrolyte with ion conductivity containing an electrolysis
solution. However, the polymer gel electrolyte may further include
the one made of polymer which has no lithium ion conductivity and
holds the same electrolysis solution among the chains thereof.
Since they are the same as the polymer gel electrolyte included in
the positive electrode layer 3, the description thereof is omitted
herein.
[0054] As described earlier, the solid polymer electrolyte and the
polymer gel electrolyte may be contained in the positive electrode
layer 3 and/or negative electrode layer 4, in addition to the
electrolyte layer 5. Different polymer electrolytes may be used for
the positive electrode layer 3, the negative electrode layer 4, and
the electrolyte 5, respectively. The same polymer electrolyte may
be used for all of the layers.
[0055] The thickness of the electrolyte layer 5 is not particularly
limited. However, in order to obtain a compact bipolar battery, the
thinnest possible layer is preferable within a thickness range that
ensures the functions of the electrolyte layer. In general, the
thickness of the solid polymer electrolyte layer is within a range
of 10 to 100 .mu.m. It is also easy to form the electrolyte layer
so as to cover top surfaces as well as the peripheral side surfaces
of the positive and negative electrode layers, while making use of
a feature of the manufacturing process. Further, the electrolyte
layer 5 is not required to have a constant thickness considering
its function and performance.
[0056] Battery Packaging Material
[0057] In the bipolar battery 20, the electrode stacked body 1 is
preferably housed in the battery packaging materials 16a and 16b or
a battery case, in order to prevent impacts from the outside while
using the battery and environmental deterioration.
[0058] From the viewpoint of lightweightness, for the battery
packaging materials 16a and 16b, it is preferable to use a battery
packaging material such as an aluminum laminate packaging material
or a polymer-metal composite laminate film, in which metal
(including alloy) such as aluminum, stainless steel, nickel, or
copper is covered with an insulating material such as a
polypropylene film. A preferable method of housing the electrode
stacked body 1 is as follows. The electrode stacked body 1 is
covered with the battery packaging materials 16a and 16b from the
top and bottom thereof, and the peripheries of the packaging
materials 16a and 16b are partially or entirely joined by thermal
welding. Therefore, the electrode stacked body 1 is housed and
sealed. The positive and negative electrode leads 23 and 24 are
sandwiched by the thermal welded portions and exposed outside of
the battery packaging materials 16a and 16b.
[0059] It is preferable to use the polymer-metal composite laminate
film, the aluminum laminate packaging material and the like, which
have excellent thermal conductivity. This is because they can
efficiently transfer heat from a heat source of a vehicle to the
inside of the battery, and can swiftly heat the inside of the
battery up to battery operating temperature.
[0060] Positive and Negative Electrode Terminal Plates
[0061] The positive and negative electrode terminal plates 14 and
15 have functions as terminals. The thinnest possible terminal
plates are preferable from the viewpoint of a thin bipolar battery.
However, since the positive and negative electrode layers 3 and 4,
the electrolyte layer 5, and the collectors 2 and 7 which construct
the electrode stacked body 1 have low mechanical strength, the
electrode terminal plates are required to have enough strength to
sandwich them from each side thereof. Additionally, in the light of
limiting electric resistance in the terminal plates, the preferable
thicknesses of the positive and negative electrode terminal plates
14 and 15 are usually within a range of 0.1 to 2 mm.
[0062] For a material of the positive and negative electrode
terminal plates 14 and 15, aluminum, copper, titanium, nickel,
stainless steel (SUS) or alloy thereof can be utilized. It is
preferable to use aluminum from the viewpoint of corrosion
resistance, manufacturability and cost efficiency.
[0063] Either the same material or different materials can be used
for the positive and negative electrode terminal plates 14 and 15.
Moreover, the positive and negative electrode terminal plates 14
and 15 may be multi-layered, formed by stacking different
materials.
[0064] As described above, the positive and negative electrode
terminal plates 14 and 15 have functions of terminals as well as
templates. To be specific, the bipolar battery of the present
invention can construct a later-described assembled battery, but
can also be used by being directly affixed to heat source such as a
motor. In the latter case, the positive and negative electrode
terminal plates can be used as templates in order to fit the shape
of the bipolar battery to the external shape of the heat source.
When using the positive and negative electrode terminal plates 14
and 15 as terminals and templates, the shapes of these terminal
plates are formed into shapes by tracing the shape of the outer
surface of the heat source of the vehicle.
[0065] Additionally, the battery packaging materials can be used as
templates instead of the terminal plates. In this case, the
terminal plates, which are provided at positions opposite the
battery packaging materials, may have the same shapes as the
collectors on which the terminal plates are placed. The shapes of
the terminal plates can be formed by press working or the like.
Note that the terminal plates, which are provided at the positions
opposite the battery packaging materials, may be formed by spray
coating similarly to the collectors.
[0066] Positive and Negative Electrode Leads
[0067] With regard to the positive and negative electrode leads 23
and 24, aluminum, copper, titanium, nickel, stainless steel (SUS),
alloy thereof or the like can be utilized. As described earlier,
the bipolar battery of the present invention is sometimes provided
directly on the heat source. In this case, a distance between the
heat source of the vehicle and both positive and negative electrode
leads 23 and 24 may become short, so that there is a possibility
that a part of each of the leads led out from the battery packaging
materials may contact with the heat source, causing leakage. Thus,
vehicle parts (especially electronic equipment) may be affected.
Hence, it is preferable that the positive and negative electrode
leads 23 and 24 are covered with heat-shrinkable tubing having
thermal-resistance and insulation.
[0068] In FIG. 5, the positive and negative electrode leads 23 and
24 are connected to the positive and negative electrode terminal
plates 14 and 15, respectively. However, the positive and negative
electrode leads 23 and 24 can be directly connected to the
collectors 7, as a matter of course.
[0069] Hereinbelow, an example of the present invention will be
described.
[0070] Evaluation of Liquid Junction
[0071] A bipolar battery similar to the one in the aforementioned
embodiment was made and liquid junction between the single cells
therein was evaluated.
[0072] The bipolar battery which was actually made as the example
is as follows.
[0073] For the collector, a stainless steel foil (SUS foil) was
used. Thickness of the stainless steel foil is about 20 .mu.m. The
positive or negative electrode layer was formed on one surface of
the end collector, and the positive and negative electrode layers
were formed on the collector.
[0074] In the positive electrode layer, LiMn.sub.2O.sub.4 was used
as the positive electrode active material, acetylene black was used
as the conductive material, polyvinylidene fluoride (PVDF) was used
as the binder, and N-methyl-2-pyrrolidone (NMP) was used as a
solvent for adjusting viscosity. These materials were mixed and
positive electrode slurry was prepared. The positive electrode
slurry was applied on one surface of the stainless steel foil,
which serves as the collector. The slurry was then dried, thus
forming the positive electrode layer.
[0075] In the negative electrode layer, Li.sub.4Ti.sub.5O.sub.12
was used as the negative electrode active material, an acetylene
black was used as the conductive material, PVDF was used as the
binder, and NMP was used as a solvent to adjust viscosity. These
materials were mixed and negative electrode slurry was prepared.
The negative electrode slurry was applied on the other surface of
the stainless steel foil on which the positive electrode layer was
applied. The slurry was then dried, thus forming the negative
electrode layer.
[0076] The polymer gel electrolyte layer was made of a 50
.mu.m-thick polypropylene (PP) nonwoven fabric holding a gel
electrolyte. The gel electrolyte contained 5 wt % of polymer
(copolymer of polyethylene oxide and polypropylene oxide), 95 wt %
of a mixed solvent (ethylene carbonate (EC): dimethyl carbonate
(DMC)=1:3) and 1.0 M of (C.sub.2F.sub.5SO.sub.2) .sub.2NLi to the
mixed solvent of EC and DMC.
[0077] For the first resin forming the sealing layer, modified
polypropylene (PP) with a melting point of 94 degrees centigrade
was used. For the second resin, polyamide-based resin with a
melting point of 200 degrees centigrade was used. The modified PP
has different degrees of polymerization, and has different melting
points from that of polyamide-based resin.
[0078] The electrode stacked body 1 was made by stacking the
collectors, the end collectors, and the polymer gel electrolyte
layers, and by providing the sealing layers between each of the
collectors. The sealing layers were formed by heating and
pressurizing the peripheries of the end collectors from the top and
the bottom thereof at 180 degrees centigrade while the single cells
were stacked. The number of stacked single cells was five.
[0079] Next, the positive and negative electrode terminal plates,
and the positive and the negative electrode leads were provided in
the electrode stacked body. The electrode stacked body thus
obtained was housed within the battery packaging materials, and the
peripheral edges of the battery packaging materials were thermally
welded, thus forming the bipolar battery shown in FIG. 4.
[0080] In addition, as a comparative example for the evaluation, a
bipolar battery with a similar construction but having no sealing
layers was formed.
[0081] Liquid junction was evaluated by conducting a
charge/discharge cycle tests of the bipolar batteries of the
example and the comparative example. One cycle of charge/discharge
includes charging current of 0.5 C and discharging current of 0.5
C.
[0082] As a result, in the bipolar battery of the example, no
liquid junction (short circuit) was observed between the electrodes
even after fifty cycles or more of charging/discharging.
[0083] On the other hand, in the bipolar battery of the comparative
example, the electrolysis solution oozed out of the single cell
layer during the first cycle of charging, and contacted with the
electrolyte layer of the other single cell layer, causing liquid
junction. Therefore, the voltage of the battery was significantly
reduced.
[0084] These evaluation results revealed that provision of the
sealing layer for each of the single cells can surely prevent
liquid junction between the single cells.
[0085] Adhesive Strength Test
[0086] Next, six stainless steel foils which construct the
collectors and the end collectors were layered with the sealing
layer placed between each of the foils, and T-type peel test was
conducted. This T-type peel test was conducted in conformity with
JIS K6854.
[0087] As for the sealing layer, two samples A and B shown in FIGS.
6A and 6B were prepared using modified PPs as the first resin,
respectively having melting points of 102, 94, and 88 degrees
centigrade, and polyamide-based resin having a melting point of 200
degrees centigrade as the second resin.
[0088] As shown in FIG. 6A, the sample A was made such that the
melting point of the first resin becomes lower as it is positioned
further inside the electrode stacked body 1. Particularly speaking,
the modified PP with the melting point of 102 degrees centigrade
was used as the first resin 10 of the outermost sealing layers 9a,
and the polyamide-based resin with the melting point of 200 degrees
centigrade was used as the second resin 11. For the subsequent
sealing layers 9b, the modified PP with the melting point of 94
degrees centigrade was used as the first resin 10 thereof, and the
polyamide-based resin with the melting point of 200 degrees
centigrade was used as the second resin 11. For the innermost
sealing layer 9c, the modified PP with the melting point of 88
degrees centigrade was used as the first resin 10 thereof, and the
polyamide-based resin with the melting point of 200 degrees
centigrade was used as the second resin 11.
[0089] As shown in FIG. 6B, the sample B was formed such that the
modified PP with the melting point of 102 degrees centigrade was
used as the first resin 10 for all the sealing layers, and the
polyamide-based resin with the melting point of 200 degrees
centigrade was used as the second resin 11.
[0090] T-type peel tests were conducted in a way that the bottom
surface of the electrode stacked body of each of these samples made
according to the above was fixed and peeled from the top.
[0091] These T-type peel tests were carried out at room temperature
(25 degrees centigrade), with a tension speed of 200 mm/min.
[0092] In sample A, the layers remained adhered to each other until
tensile strength reached 54N/25 mm. On the other hand, in sample B,
the middle layer was peeled off at 35N/25 mm.
[0093] This test was conducted twenty times, and the layer in the
middle of sample B always peeled off as shown in FIG. 7. On the
contrary, the layers in sample A randomly peeled off when forces of
54N/25 mm or more were applied.
[0094] According to the above, it is considered possible to adhere
a plurality of stacked stainless steel foils with an uniform
strength by using the first resin 10 having different melting
points in each of the sealing layers 9 such that the melting points
of the first resin 10 rise from the middle toward the outside.
[0095] According to the first embodiment and the example to which
the present invention is applied, in the battery having a plurality
of stacked single cells 6, provision of the sealing layers 9 for
each of the single cells 6 prevents liquid junction between the
single cells 6, and a highly durable and reliable battery can be
provided.
[0096] Second Embodiment
[0097] A second embodiment of the present invention is an assembled
battery in which the plurality of the bipolar batteries 20 of the
foregoing first embodiment is connected to each other.
[0098] As shown in FIGS. 8 and 9, in this assembled battery 50, the
plurality of bipolar batteries 20 of the foregoing first embodiment
which is connected in series is further connected in parallel.
Between the bipolar batteries 20, the positive electrode leads 23
and the negative electrode leads 24 of each of the batteries are
connected by conductive members 53. The plurality of bipolar
batteries which is electrically connected is connected to terminals
51 and 52 provided on one side surface of the assembled battery
50.
[0099] In this assembled battery 50, the terminals of the batteries
20 and the conductive members 53 can be connected using a method
such as ultrasonic welding, heat welding, laser welding, rivet,
crimping and electron beam. By using such a connecting method, it
is possible to manufacture a battery having long-term
reliability.
[0100] According to the assembled battery of the second embodiment,
it is possible to obtain the assembled battery with a high capacity
and high power by using the batteries of the foregoing first
embodiment to form the assembled battery. In addition, since each
of the batteries is highly reliable, the assembled battery having a
long-term reliability can be further improved.
[0101] With regard to the connection of the batteries 20 as the
assembled battery, all of the plurality of batteries 20 may be
connected in parallel, and alternatively, all of the plurality of
batteries 20 may be connected in series.
[0102] Third Embodiment
[0103] A third embodiment is an assembled battery module in which
the plurality of assembled batteries of the aforementioned second
embodiment are connected to each other.
[0104] As shown in FIG. 10, the assembled battery module 60 is
formed into a module in a way that the plurality of assembled
batteries 50 of the foregoing second embodiment are stacked, and
the terminals 51 and 52 of each of the assembled batteries 50 are
connected by conductive members 61 and 62.
[0105] The modularization of the assembled batteries 50 in this way
facilitates battery control and forms an optimal assembled battery
module to be mounted on a vehicle such as an electric vehicle and a
hybrid vehicle. The assembled battery module 60 has a long-term
reliability since the foregoing assembled batteries are used
therefor.
[0106] Fourth Embodiment
[0107] A fourth embodiment is a vehicle which mounts the assembled
battery module according to the aforementioned third embodiment and
uses the assembled battery module as a power source of a motor. The
vehicle using the assembled battery module as the power source for
the motor is, for example, an electric vehicle and a hybrid
vehicle, in which wheels are driven by the motor.
[0108] For reference, FIG. 11 shows a vehicle 100 having the
assembled battery module 60 mounted thereon. The assembled battery
module 60 mounted on the vehicle has the characteristics described
earlier. Therefore, the vehicle on which the assembled battery
module 60 is mounted has high durability and is capable of
providing sufficient power over a long period of time.
[0109] The entire content of a Japanese Patent Application No.
P2002-323971 with a filing date of Nov. 7, 2002 is herein
incorporated by reference.
[0110] Although the invention has been described above by reference
to certain embodiments of the invention, the invention is not
limited to the embodiments described above will occur to these
skilled in the art, in light of the teachings. The scope of the
invention is defined with reference to the following claims.
* * * * *